Elastic cover and removable cone assembly



June 2, 1970 J. AJSIEVERT i 3,515,798

' ELASTIC COVER AND REMOVABLE CORE ASSEMBLY I Filed Dec. 6, 1968 I NVENTOR.

MAME; A. S/EVEPT BY M M {do /4M ATTORNE Y$ United States Patent3,515,798 ELASTIC COVER AND REMOVABLE CONE ASSEMBLY James A. Sievert,Stillwater, Minn., assignor to Minnesota Mining and ManufacturingCompany, St. Paul, Minn., a corporation of Delaware Filed Dec. 6, 1968,Ser. No. 781,843

, Int. Cl. H01r 5/00 U.S. Cl. 174-135 6 Claims ABSTRACT OF THEDISCLOSURE An elastic tubular cover member supported in stretchedcondition on an easily removable one-piece rigid spiral core havinginterconnected adjacent coils. Uncoiling of the spiral and removal ofthe core as a continuous narrow strip through the remainder of thespiral permits the cover to be shrink fit upon a workpiece disposedwithin the assembly.

U.S. Pat. No. 743,346 wherein a soft rubber cover is formed on a metalsleeve which unites the wire-ends. Other forms have been described, e.g.in Dibner U.S. Pat. No. 2,674,647 and in Becker et al. U.S. Pat. No.3,274,- 330. Heat-retractable normally non-elastic coverings have alsobeen used, as in Foreit U.S. Pat. No. 2,695,853, although providing aless elfective cover because of their inability to retract at normal usetemperatures after stretching. In a diflerent area, tough elasticrubbery rings or sleeves used as protectors for drill pipes have beensupplied in expanded or stretched form on removable rigid sleeves, asshown for example in Gates U.S. Pat. No. 2,725,621 and Stone et al. U.S.Pat. No. 2,682,102.

Thepresent invention likewise provides a rubbery or elasticallyshrinkable tubular cover member supported in radially expanded orstretched condition on a removable rigid sleeve, but having a number ofadvantages. Removal of the sleeve in applying the cover is easilyaccomplished without the use of complicated or expensive presses orother machines and may be effected by simple hand operation. Thesupporting sleeve is easily and completely removable from any positionand need not be removed at an end of the wire, tube, or other articleonto which the rubbery cover is to be permitted to contract. Nolubricants or friction-reducing materials are required to facilitateremoval of the support.

These and other advantages are obtained, in accordance with theprinciples of the invention, by employing as the removable rigidsupporting core a tubular member having a closed helix configuration aswill now be further described in connection with the appended drawing.The single figure is an illustration in elavation and partly in sectionshowing the application of a protective rubbery sleeve to a cable splicearea.

The illustration shows two cable-ends 11 comprising a stranded conductor12 and an insulating covering 13. The covering is cut away as at 14 andthe conductors joined together in end-to-end configuration by suitablemeans not shown but which may typically consist of a com- Patented June2, 1970 pressed or indented metal sleeve or a close-fitting metal tubewith set-screws retainers. The joint or splic may be covered withinsulating mastic or tape, here omitted for clarity of illustration.

The cover assembly is slipped over one of the wire-ends prior to joiningthe two ends. After the splice is completed, the assembly is slid intoposition over the splice area and the support is removed to permit theelastic cover to contract and form a tight fit. The process will beapparent from the illustration. The support comprises a unitary tubularshell 15 helically grooved along its entire length, the continuousgroove 16 permitting the shell to be pulled out into a continuous strip17 which is removed through the bore, i.e. from between the shell andthe cable. An elastic tube 18 in radially extended or strtched conditionis supported on the shell 15. As the strip 17 is progressivelywithdrawn, the tube contracts about the cable as at 19 to form a closelyconforming and tightly retained protective covering. Contraction of thetube results in the application of a resultant force against the end ofthe shell and assists in the removal of the strip 17 as the shell isunwound.

In an illustrative embodiment a cylindrical tube of age-resistanttranslucent vulcanized rubber which in the relaxed state has an insidediameter of about 15 mm. and a'wall thickness of about 3 mm. is mountedon a rigid cylindrical tubular core of tough flexible cellulose acetatebutyrate or polyvinyl chloride polymer material having an outsidediameter of about 30 mm. and a wall thickness of about 2 mm. andspirally grooved in a narrow V-shaped groove approximately 1.5 mm. indepth and at a spacing of about 4 mm., the adjacent coils of the closedhelix defined by the groove remaining interconnected. The assembly isslipped over a cable splice area having a diameter of about 20 mm. andthe core is unwound and removed as a continuous narrow strip frombetween the core and the cable in the manner illustrated. Hand pullingprovides fully adequate tension to unwind the core and remove the strip,leaving the rubber tube tightly aflixed to the cable. It will beappreciated that the polymeric tube in effect is substantially rigid andmaintains its tubular shape, even though the material of which it isconstructed is sufficiently tough and flexible to permit unwinding andremoval of the helical strip under the tension supplied.

Synthetic rubbers and other elastic materials may be used in place ofnatural rubber, and the coverings may be suitably compounded or treatedin any desired manner, for example by the incorporation of opacifying ortoughening pigments such as carbon black or zinc oxide, antioxidants,vulcanizing agents, processing oils, and other well-known compoundingagents, and by heatcuring or other treatments. Suitable identifyingmarkings or legends may be applied. As a further specific illustration,conductive platelets may be incorporated, as taught in Wyatt U.S. Pat.No. 3,349,164, to provide an elastic insulative stress relief covering.

Although not essential to the application of the elastic covering, insome instances it may be found desirable to pre-coat the cable splicearea, for example with a prim ing or water-proofing coating or awrapping of adhesive tape. Alternatively, the inner surface of theelastic tube may itself carry a thin coating, for example ofpressure-sensitive adhesive or of silicone gum for improving the bond orwater-resistance between the tube and the cable. In such instances itmay be found expedient to cover the external surface of the supportingshell, either before or after the forming of the helical groove, with alow adhesion backsize composition.

The elasticity of the rubbery tube not only retains the tube firmly onthe core and assists in the unwinding and removal of the core, butadditionally assists in holding the coils of the helix together, i.e. inthe form of a closed helix, until they are forcefully removed by pullingon the extended end of the strip. Consequently the groove may be made asdeep as desired for ease of separation of the coils, without fear ofpremature collapse of the structure.

Both the elastic sleeve and the rigid supporting core are ordinarilycylindrical both for ease of manufacture and as being of maximumutility, but tubular structures of non-uniform diameter are alsocontemplated as coming within the purview of the invention, a specificexample being a conical structure for use as an end cap on a cabletermination.

What is claimed is as follows:

1. An elastic cover assembly comprising an elastic cover membersupported in highly stretched condition on a hollow core membercomprising a continuous narrow strip of tough flexible material in theform of a substantially rigid closed helix having adjacent coilsinterconnected.

2. The assembly of claim 1 wherein said core member is a deeply spirallygrooved polymeric tube, the groove being. sufficiently deep to permitseparation of the interconnected adjacent coils defined thereby forremoval as a continuous narrow strip remainder of said tube.

3. The assembly of claim 2 wherein said polymeric tube is of celluloseacetae butyrate or polyvinyl chloride and said groove extends throughabout three-fourths the wall thickness of said tube.

'4. The assembly of claim 1 wherein said cover member carries over itsinner surface a thin water-resistant coating.

5. The assembly of claim 4 wherein said coating is a pressure-sensitiveadhesive.

6. The assembly of claim 4 wherein said coating is a silicone.

extending through the References Cited I FOREIGN PATENTS 189,460 4/1957Austria.

OTHER REFERENCES German printed application No. 1,053,602, Schwarzer,published Mar. 26, 1959.

LARAMIE E. ASKIN, Primary Examiner U.S. Cl. X.R.

